Morphological and morphometric features of nematode-cysts in Gymnotus inaequilabiatus liver in the Brazilian Pantanal

Abstract

The aim of this study was to determine the morphometric measures and morphological aspects of nematode-cysts in Gymnotus inaequilabiatus, and the presence of melanomacrophage centers (MMCs) associated with the periphery of cysts and in the liver parenchyma. Adult specimens, 34 female (123.1 ± 43.9g) and 45 male (135.5 ± 43.4g), from Paraguay River, Corumbá, Brazil, were used. The number of nematode-cysts was determined in 79 livers and 25 of them randomly selected for histopathological analysis and morphometric measures of nematode-cysts (mean diameter, thickness of collagen layer, and cyst-wall layer). The percentage of cysts with MMCs on the periphery and density in the liver parenchyma was estimated. The average number of macroscopic cysts was of 48.7 ± 2.78. Granulomatous reaction was observed surrounding the cysts. Diameter, collagen layer and cyst-wall measurements were 293.0 ± 75.18 (µm), 17.72 ± 6.01 (µm) and 12.21 ± 9.51 (µm), respectively. The number of nematode-cysts was correlated with hepatosomatic index, (r=0.26, P<0.05). Collagen layer was correlated with cyst diameter (r=0.62, P<0.01). Pericystic and parenchymatous MMCs were moderately (r=0.48) and highly (r=0.90) correlated with nematode-cysts number. Morphological characteristics of hepatic tissue and cysts-nematodes measures suggest that G. inaequilabiatus acts as a paratenic host to nematodes in the larval stage.Keywords: Brevimulticaecum sp., Gymnotiformes, nematoda, melanomacrophages. ResumoO objetivo deste estudo foi determinar as características morfológicas e morfométricas de cistos de nematodas em fígado de Gymnotus inaequilabiatus, e a presença de centros de melanomacrófagos (CMMs) pericísticos e no parênquima hepático. Espécimes adultos, 34 fêmeas (123,1 ± 43,9 g) e 45 machos (135,5 ± 43,4g), provenientes do Rio Paraguai, Corumbá, Brasil foram utilizados. Os cistos foram quantificados em 79 fígados. Em 25 fígados foi realizada a análise histopatológica e morfometria dos cistos (diâmetro, espessura da camada de colágeno e da parede). Estimou-se a porcentagem de cistos com CMMs periférico e a densidade de CMMs no parênquima. A média de cistos macroscópicos foi de 48,7 ± 2,78. Observou-se reação granulomatosa pericística. O diâmetro, a espessura da camada de colágeno e da parede do cisto foi de 293,0 ± 75,18 (µm), 17,72 ± 6,01 (µm) e 12,21 ± 9,51 (µm), respectivamente. O número de cistos foi associado ao índice hepatossomático, (r=0,26, P <0,05). A camada de colágeno correlacionou-se com o diâmetro do cisto (r=0,62, P <0,01). CMMs pericísticos e do parênquima apresentaram correlação moderada (r=0,48) e alta (r=0,90) com o número de cistos, respectivamente. As características morfológicas do tecido hepático e a morfometria dos cistos de nematodas sugerem que G. inaequilabiatus atua como hospedeiro paratênico para larvas de nematodas.Palavras-chave: Brevimulticaecum sp., Gymnotiformes, nematoda, melanomacrófagos.

Kidney anatomy, histology and histometric traits associated to renosomatic index in Gymnotus inaequilabiatus (Gymnotiformes: Gymnotidae)

“…The coefficient measured between gross lesions and RSI suggests that adult or aged specimens with higher indices would tend to sustain more injuries through the organ. The negative correlations with MMCs may be due to these structures remaining aggregated around the granulomatous lesions and moderately dispersed in the renal parenchyma, a feature previously reported to hepatic nematode-cysts granulomas (Galindo et al, 2017). In the present study, MMCs account for a substantial fraction of the volumetric density in both the head and exocrine kidney mostly composed of melanin (Agius, Roberts, 2003;Kumar et al, 2016).…”

“…These conditions are characterized by low oxygen level, which probably induces anatomical and functional adaptations, such as breathing air through accessory airbreathing organs or via gill system (Crampton, 1998;Moraes et al, 2002). Furthermore, fish are subjected to adverse situations such as large temperature fluctuations, food scarcity, and a broad spectrum of pathological agents (Bonga, 1997;Galindo et al, 2017).…”

“…The Gymnotidae family has been studied from the genetic, taxonomic, endoparasitic fauna and ecological standpoints (Willink et al, 2000;Albert et al, 2005;Scacchetti et al, 2011;Galindo et al, 2017). Although these studies are numerous, there are no reports about anatomy, histology, and histopathological features of the kidney and were not even reported biometrics and histometric traits in this species.…”

ENDOPARASITOS DE Gymnotus sp. (GYMNOTIFORMES: GYMNOTIDAE) DE ISQUEIROS COMERCIAIS NA BACIA DO PANTANAL, BRASIL CENTRAL

“…in fish are scarce. To date, Brevimulticaecum larvae have been reported in the celomatic cavity, hepatic parenchyma, mesentery, skeletal muscle and stomach wall of Gymnotus inaequilabiatus (VIEIRA et al, 2010) and GALINDO et al (2017) suggest that G. inaequilabiatus acts as a paratenic host to nematodes in the larval stage.…”

Characterization of ecto- and endoparasite communities of wild Mediterranean teleosts by a metabarcoding approach

“…A lot of parasites, such as helminths or copepods, go through different life stages (i.e. cyst, egg and larval stages) [14–17] that are often difficult or nearly impossible to locate [18] and even if some of them can be detected, morphological differences are insufficient to differentiate between species from these development stages [19–20]. In addition, these surveys usually focus on a single class of parasites, ecto- or endoparasites [21–24] and sometimes even on specific genera [25–27].…”